untangle the "need_reval_dot" mess

instead of ad-hackery around need_reval_dot(), do the following:
set a flag (LOOKUP_JUMPED) in the beginning of path, on absolute
symlink traversal, on ".." and on procfs-style symlinks.  Clear on
normal components, leave unchanged on ".".  Non-nested callers of
link_path_walk() call handle_reval_path(), which checks that flag
is set and that fs does want the final revalidate thing, then does
->d_revalidate().  In link_path_walk() all the return_reval stuff
is gone.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 44 insertions, 63 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 4521b5ff7c93..450b686e9682 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -613,19 +613,8 @@ do_revalidate_rcu(struct dentry *dentry, struct nameidata *nd)
         return dentry;
 }
 
-static inline int need_reval_dot(struct dentry *dentry)
-{
-        if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
-                return 0;
-
-        if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
-                return 0;
-
-        return 1;
-}
-
 /*
- * force_reval_path - force revalidation of a dentry
+ * handle_reval_path - force revalidation of a dentry
  *
  * In some situations the path walking code will trust dentries without
  * revalidating them. This causes problems for filesystems that depend on
@@ -639,27 +628,28 @@ static inline int need_reval_dot(struct dentry *dentry)
  * invalidate the dentry. It's up to the caller to handle putting references
  * to the path if necessary.
  */
-static int
-force_reval_path(struct path *path, struct nameidata *nd)
+static inline int handle_reval_path(struct nameidata *nd)
 {
+        struct dentry *dentry = nd->path.dentry;
         int status;
-        struct dentry *dentry = path->dentry;
 
-        /*
-         * only check on filesystems where it's possible for the dentry to
-         * become stale.
-         */
-        if (!need_reval_dot(dentry))
+        if (likely(!(nd->flags & LOOKUP_JUMPED)))
+                return 0;
+
+        if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
                 return 0;
 
+        if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
+                return 0;
+
+        /* Note: we do not d_invalidate() */
         status = d_revalidate(dentry, nd);
         if (status > 0)
                 return 0;
 
-        if (!status) {
-                d_invalidate(dentry);
+        if (!status)
                 status = -ESTALE;
-        }
+
         return status;
 }
 
@@ -728,6 +718,7 @@ static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *l
                 path_put(&nd->path);
                 nd->path = nd->root;
                 path_get(&nd->root);
+                nd->flags |= LOOKUP_JUMPED;
         }
         nd->inode = nd->path.dentry->d_inode;
 
@@ -779,11 +770,8 @@ __do_follow_link(const struct path *link, struct nameidata *nd, void **p)
                 error = 0;
                 if (s)
                         error = __vfs_follow_link(nd, s);
-                else if (nd->last_type == LAST_BIND) {
-                        error = force_reval_path(&nd->path, nd);
-                        if (error)
-                                path_put(&nd->path);
-                }
+                else if (nd->last_type == LAST_BIND)
+                        nd->flags |= LOOKUP_JUMPED;
         }
         return error;
 }
@@ -1351,7 +1339,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
         while (*name=='/')
                 name++;
         if (!*name)
-                goto return_reval;
+                goto return_base;
 
         if (nd->depth)
                 lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
@@ -1385,12 +1373,16 @@ static int link_path_walk(const char *name, struct nameidata *nd)
                 type = LAST_NORM;
                 if (this.name[0] == '.') switch (this.len) {
                         case 2:
-                                if (this.name[1] == '.')
+                                if (this.name[1] == '.') {
                                         type = LAST_DOTDOT;
+                                        nd->flags |= LOOKUP_JUMPED;
+                                }
                                 break;
                         case 1:
                                 type = LAST_DOT;
                 }
+                if (likely(type == LAST_NORM))
+                        nd->flags &= ~LOOKUP_JUMPED;
 
                 /* remove trailing slashes? */
                 if (!c)
@@ -1456,7 +1448,7 @@ last_component:
                                 } else
                                         follow_dotdot(nd);
                         }
-                        goto return_reval;
+                        goto return_base;
                 }
                 err = do_lookup(nd, &this, &next, &inode);
                 if (err)
@@ -1483,24 +1475,6 @@ last_component:
 lookup_parent:
                 nd->last = this;
                 nd->last_type = type;
-                if (type == LAST_NORM)
-                        goto return_base;
-return_reval:
-                /*
-                 * We bypassed the ordinary revalidation routines.
-                 * We may need to check the cached dentry for staleness.
-                 */
-                if (need_reval_dot(nd->path.dentry)) {
-                        if (nameidata_drop_rcu_last_maybe(nd))
-                                return -ECHILD;
-                        /* Note: we do not d_invalidate() */
-                        err = d_revalidate(nd->path.dentry, nd);
-                        if (!err)
-                                err = -ESTALE;
-                        if (err < 0)
-                                break;
-                        return 0;
-                }
 return_base:
                 if (nameidata_drop_rcu_last_maybe(nd))
                         return -ECHILD;
@@ -1523,7 +1497,7 @@ static int path_init(int dfd, const char *name, unsigned int flags, struct namei
         struct file *file;
 
         nd->last_type = LAST_ROOT; /* if there are only slashes... */
-        nd->flags = flags;
+        nd->flags = flags | LOOKUP_JUMPED;
         nd->depth = 0;
         nd->root.mnt = NULL;
         nd->file = NULL;
@@ -1630,6 +1604,9 @@ static int path_lookupat(int dfd, const char *name,
                 br_read_unlock(vfsmount_lock);
         }
 
+        if (!retval)
+                retval = handle_reval_path(nd);
+
         if (nd->file) {
                 fput(nd->file);
                 nd->file = NULL;
@@ -1690,7 +1667,7 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
 
         /* same as do_path_lookup */
         nd->last_type = LAST_ROOT;
-        nd->flags = flags;
+        nd->flags = flags | LOOKUP_JUMPED;
         nd->depth = 0;
 
         nd->path.dentry = dentry;
@@ -1703,6 +1680,8 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
         current->total_link_count = 0;
 
         result = link_path_walk(name, nd);
+        if (!result)
+                result = handle_reval_path(nd);
         if (result == -ESTALE) {
                 /* nd->path had been dropped */
                 current->total_link_count = 0;
@@ -1710,8 +1689,11 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
                 nd->path.mnt = mnt;
                 nd->inode = dentry->d_inode;
                 path_get(&nd->path);
-                nd->flags |= LOOKUP_REVAL;
+                nd->flags = flags | LOOKUP_JUMPED | LOOKUP_REVAL;
+
                 result = link_path_walk(name, nd);
+                if (!result)
+                        result = handle_reval_path(nd);
         }
         if (unlikely(!result && !audit_dummy_context() && nd->path.dentry &&
                                 nd->inode))
@@ -2198,30 +2180,29 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
 {
         struct dentry *dir = nd->path.dentry;
         struct file *filp;
-        int error = -EISDIR;
+        int error;
 
         switch (nd->last_type) {
         case LAST_DOTDOT:
                 follow_dotdot(nd);
                 dir = nd->path.dentry;
         case LAST_DOT:
-                if (need_reval_dot(dir)) {
-                        int status = d_revalidate(nd->path.dentry, nd);
-                        if (!status)
-                                status = -ESTALE;
-                        if (status < 0) {
-                                error = status;
-                                goto exit;
-                        }
-                }
                 /* fallthrough */
         case LAST_ROOT:
+                error = handle_reval_path(nd);
+                if (error)
+                        goto exit;
+                error = -EISDIR;
                 goto exit;
         case LAST_BIND:
+                error = handle_reval_path(nd);
+                if (error)
+                        goto exit;
                 audit_inode(pathname, dir);
                 goto ok;
         }
 
+        error = -EISDIR;
         /* trailing slashes? */
         if (nd->last.name[nd->last.len])
                 goto exit;
@@ -2422,7 +2403,7 @@ reval:
         /*
          * We have the parent and last component.
          */
-        nd.flags = flags;
+        nd.flags = (nd.flags & ~LOOKUP_PARENT) | flags;
         filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);
         while (unlikely(!filp)) { /* trailing symlink */
                 struct path link = path;